The paper provides a comparative history of the economic impact of the Revolutionary and Napoleonic Wars. By focusing on the relative price evidence, it is possible to show that the conflict had major economic effects around the world. Britain's control of the seas meant that it was much less affected than other nations, such as France and the United States. Explicit welfare calculations are provided for four countries, Britain, France, Sweden and the United States. Welfare losses were largest in the US, where they were of the order of 5-6% per annum; by contrast, they lay between 3-4% per annum in France, and between 1.7-1.8% per annum in Britain. On the other hand, the conflict helped pave the way for the more liberal international economic environment of the long 19th century.